Fast lane

Joining steel and aluminum

Mazda Motor Corporation has developed the world’s first direct spot joining technology to join steel and aluminum. The technology has evolved, and will be used to join the trunk lid and bolt retainer for the updated and improved Mazda MX-5 sports car that is scheduled to go on sale around the world in the latter half of 2005. Up to now, welding two different metals such as steel and aluminum has been a difficult task. However, by optimising the rotating tool shape and joining characteristics, and by using galvanized steel on one side, joining steel and aluminum has been made possible. The process is similar to that of joining two pieces of aluminum, when a joining gun holds the parts from both sides with a welding tool. The joining tool is then made to spin while force is applied, which in turn generates frictional heat that subsequently joins the aluminum materials to the steel sheet metal. Galvanized steel helps prevent the galvanic corrosion that results from the contact of two different types of metal. Compared with conventional joining techniques such as riveting or clinching, steel and aluminum spot friction welding makes it easier to join materials that are difficult to deform, such as aluminum casting and high tensile steel. Additionally, running costs can be reduced because riveting becomes unnecessary. This innovative technology makes it simple to join steel and aluminum, and improves the potential of coupling aluminum parts to steel in vehicle bodies, and has other applications in a wide range of industrial uses. The process contributed significantly to Mazda’s vehicle weight reduction efforts during the development of the MX-5 sports car, where each gram was counted, as well as lowering costs. Mazda has applied for over twenty patents related to this technology.

High-pressure hydrogen tank for fuel-cell vehicles

Toyota Motor Corporation (TMC) has said that it has developed 35MPa and 70MPa high-pressure hydrogen tanks for use in fuel cell vehicles. Additionally, the 35MPa tank can be used for 15 years, compared to three years for previous tanks. The new Toyota high pressure hydrogen tanks employ an anti-leak liner made of high-strength nylon resin with superior hydrogen permeation-prevention performance. The tanks also feature an all-composite structure concealed by a carbon fibre exterior, making them light and extremely strong. The use of a nylon resin tank liner allows the liner to be thinner, meaning that the new 35MPa tank can hold 10 per cent more hydrogen than the same-exterior-size 35MPa tank Toyota used before. This extends the cruising range of Toyota’s hydrogen-fueled Toyota FCHV fuel cell hybrid passenger vehicle from 300km to 330km. Furthermore, the 70MPa tank, also designed and sized for the Toyota FCHV, can store approximately 1.7 times more hydrogen than the previous 35MPa tank, resulting in a cruising range of more than 500km.

Both tanks feature a high-pressure valve developed anew within the Toyota Group. This valve follows a new design that positions a solenoid shut-off valve inside the tank for increased reliability.